Two mono‐ and dinuclear Bi(III) complexes, [Bi(L)2(NO3)2]·NO3 (1) and [Bi2(L)2Cl8] (2) (L = (2‐(2‐pyridyl)‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide), were obtained via complexation of L with Bi(III) nitrate pentahydrate and Bi(III) chloride. L and both complexes were characterized by elemental analyses and spectroscopic methods including FT‐IR, UV–Vis, and fluorescence spectroscopy. Specifically, it clearly manifested that both complexes had good fluorescence emission and showed different fluorescence behaviors in diverse solvents. Both Bi(III) complexes were further determined by X‐ray crystallography, and it was found that the ratio of ligand to metal was 2:1 in 1, whereas 2 was 1:1. Their coordination geometric configurations were significantly different, such as octa‐coordinated complex 1 formed an infinite 1‐D chain‐like, funnel‐shaped 2‐D network, and ladder‐like 3‐D supramolecular framework, whereas hexa‐coordinated complex 2 with a binuclear structure exhibited two slightly distorted octahedral geometric structures; meanwhile, symmetric units came into being an infinite 2‐D layer even and meter‐shaped 3‐D supramolecular skeleton. The optimal geometries, frontier molecular orbital energies, and molecular electrostatic potential diagrams of both complexes were calculated using DFT/B3LYP. The electronic distribution of HOMO‐LUMO rationalized the results of UV–Vis spectra with the help of TD‐DFT calculations. Furthermore, all samples demonstrated excellent antibacterial activities against Escherichia coli and Staphylococcus aureus. In addition, non‐covalent interactions of complexes and their contributions were quantified with Hirshfeld surfaces using CrystalExplorer17 program.

Two mononuclear and dinuclear octahedral complexes, [Mn(L1)2Cl2] (1) and [Bi2(L2)2Cl8] (2) (L1 = 2‐(2‐pyridyl)‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide, L2 = 2‐(3‐pyridyl)‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide) were prepared by natural volatilization method. The ligands and both complexes were compared with spectroscopic methods, as well as characterized by elemental analysis. The photoluminescence behaviors of both complexes in different solvents were also investigated. The coordination possibility of ligands toward Mn (II)/Bi (III) was verified using X‐ray crystallography, and it revealed that the ratio of ligand to metal was 2:1 in 1, whereas 1:1 in 2. The adjacent molecules of six‐coordinated complex 1 constituted an infinite 1‐D chain, 2‐D network, and ladder‐like 3‐D supramolecular frameworks. Most strikingly, hexa‐coordinated complex 2 with dinuclear structure formed an infinite 1‐D chain, 2‐D layered and meter‐shaped 3‐D supramolecular skeleton. Density functional theory (DFT) calculation was used to optimize the geometry of complexes, compute the electrostatic potential diagrams, and evaluate the HOMO‐LUMO energy gap. The electronic transition simulated through time‐dependent (TD)‐DFT level of calculation rationalized the experimental data. The antibacterial properties of all compounds were evaluated against Gram‐positive and Gram‐negative bacterial strains. In addition, the Hirshfeld surface was utilized to quantify some hydrogen bonding interactions and their contributions.